Eric Magnus Campbell Tigerstedt (August 4, 1887 – April 20, 1925) was one of the most significant inventors in Finland at the beginning of the 20th century, and has been called the "
Thomas EdisonThomas Alva Edison was an American inventor, scientist and businessman who developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb...
of Finland". He was the first person to implement a working
sound-on-filmA sound film is a motion picture with synchronized sound, or sound technologically coupled to image, as opposed to a silent film. The first known public exhibition of projected sound films took place in Paris in 1900, but decades would pass before reliable synchronization was made commercially...
technology, and in the process, he made significant improvements to the amplification properties of the
vacuum valveIn electronics, a vacuum tube, electron tube , thermionic valve, or valve is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space...
. Having seen a showing of the Lumière brothers new motion picture technology as a 9-year old boy in Helsinki in 1896, he was inspired to bring sound to silent pictures.
Many years later, his own film "Word and Picture" was presented to a gathering of scientific dignitaries in Berlin in 1914. It was the world's first successful "talking picture", although his technology was never commercialised. Apart from improving on the design of the triode vacuum valve, he also developed directional loudspeakers. Tigerstedt also predicted such future inventions as the television and the mobile phone, and in 1917, he filed a patent for what he described as a "pocket-size, folding telephone with a very thin carbon microphone". Tigerstedt was awarded a total of 71 patents in several countries between the years 1912 and 1924.
Early interest in technology
Tigerstedt was born in
HelsinkiHelsinki is the capital and largest city in Finland. It is in the southern part of Finland, on the shore of the Gulf of Finland, by the Baltic Sea. The population of the city of Helsinki is , making it the most populous municipality in Finland by a wide margin...
and started to show a particular interest in all things technical already at an early age. He studied his father’s scientific books with great interest, and at age 11, built a simple photographic
deviceA broad definition of a tool is an entity used to interface between two or more domains that facilitates more effective action of one domain upon the other. The most basic tools are simple machines. For example, a crowbar simply functions as a lever. The further out from the pivot point, the more...
. At age 13, he began experimenting with other technical devices and machines, and he built his own version of an
electric motorAn electric motor uses electrical energy to produce mechanical energy, usually through the interaction of magnetic fields and current-carrying conductors. The reverse process, producing electrical energy from mechanical energy, is accomplished by a generator or dynamo. Traction motors used on...
and electrical
batteriesAn electrical battery is a combination of one or more electrochemical cells, used to convert stored chemical energy into electrical energy. Since the invention of the first Voltaic pile in 1800 by Alessandro Volta, the battery has become a common power source for many household and industrial...
. After a fall-out with his father, he left home at the age of 15, and supported himself by working as a handyman and technician in mechanical workshops and
shipyardShipyards and dockyards are places which repair and build ships. These can be yachts, military vessels, cruise liners or other cargo or passenger ships. Dockyards are sometimes more associated with maintenance and basing activities than shipyards, which are sometimes associated more with initial...
s in Helsinki. He later worked as a
technicianA technician is generally someone in a technological field who has a relatively practical understanding of the general theoretical principles of that field, e.g., as compared to an engineer in that field. They are generally much more versed in technique compared to the average layman, or even the...
in the
telephoneThe telephone is a telecommunications device that transmits and receives sound, most commonly the human voice. It is one of the most common household appliances in the developed world, and has long been considered indispensable to business, industry and government...
industry, which was rapidly becoming a major business in Helsinki at this time.
Studies in Germany
In 1908 Tigerstedt moved to
GermanyGermany , officially the Federal Republic of Germany , is a country in Central Europe. It is bordered to the north by the North Sea, Denmark, and the Baltic Sea; to the east by Poland and the Czech Republic; to the south by Austria and Switzerland; and to the west by France, Luxembourg, Belgium,...
to continue his studies. He completed his high school
educationEducation in its broadest sense is any act or experience that has a formative effect on the mind, character or physical ability of an individual...
, and began studies in
electrical engineeringElectrical engineering, sometimes referred to as electrical and electronic engineering, is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after...
at the Friedrichs Polytechnikum in Cöthen (Köthen). After completing his studies there in 1911, he moved back to Finland with his fiancée Marjatta Nybom, whom he had met and fallen in love with while in Köthen. She had been studying the violin in
SwitzerlandSwitzerland , officially the Swiss Confederation , is a federal republic consisting of 26 states named cantons, with Bern as the seat of the federal authorities...
and had met Tigersted through her brother Albert Nybom, who was also studying in Köthen and who was a class mate of Tigerstedt. However, the engagement between Tigerstedt and Marjatta Nybom was broken off in 1912.
First Sound-On-Film prototype
After having returned to Finland, he continued his experiments, and succeeded in building a prototype of
sound-on-filmSound-on-film refers to a class of sound film processes where the sound accompanying picture is physically recorded onto photographic film, usually, but not always, the same strip of film carrying the picture. Sound-on-film processes can either record an analog sound track or digital sound track,...
technology ("talking movies"). Tigerstedt then returned to Germany in 1913, and founded a company with the Swedish merchant Axel Wahlstedt and the Swedish engineer Hugo Swartling. This was the first in a series of unsuccessful business ventures. Although Tigerstedt was able to complete his work with the sound-on-film technology, their
laboratoryA laboratory is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. The title of laboratory is also used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories...
was ultimately confiscated due to unpaid rent. They later managed to recuperate their laboratory, but it was finally destroyed in a fire. The cooperation between Wahlstedt and Tigerstedt also become strained, and in January 1914 they unwound their company. After breaking off their connercial partnership, Wahlstedt returned to Sweden while Tigerstedt stayed behind in Berlin, more or less broke.
First demonstration of Sound-On-Film
Tigerstedt continued working on his sound-on-film technology, and during the process, he managed to solve a major technical problem, that of how to amplify film audio in a large
theatre hallTheatre is a branch of the performing arts. While any performance may be considered theatre, as a performing art, it focuses almost exclusively on live performers creating a self contained drama. A performance qualifies as dramatic by creating a representational illusion...
. He did this by making major improvements to the vacuum tube design of
Lee De ForestLee De Forest was an American inventor with over 180 patents to his credit. De Forest invented the Audion, a vacuum tube that takes relatively weak electrical signals and amplifies them. De Forest is one of the fathers of the "electronic age", as the Audion helped to usher in the widespread use...
, increasing the
amplificationGenerally, an amplifier or simply amp, is any device that changes, usually increases, the amplitude of a signal. The relationship of the input to the output of an amplifier—usually expressed as a function of the input frequency—is called the transfer function of the amplifier, and the magnitude of...
properties several times. In February/March 1914, Tigerstedt demonstrated his sound-on-film technology to a small group of scientists, using his own film "Word and Picture”.
1914-1917
After having been expelled from Germany in July 1914, Tigerstedt returned to Finland, but moved to
SwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe...
a few months later, and then finally to
DenmarkDenmark is a Scandinavian country in Northern Europe and the senior member of the Kingdom of Denmark. It is the southernmost of the Nordic countries; southwest of Sweden and south of Norway, and it is bordered to the south by Germany. Denmark borders both the Baltic and the North Sea...
in 1915. After another unsuccessful business venture, Tigerstedt once more returned to Finland. In 1917, he moved back to Denmark, founded yet another company, which was then sold. After this, he participated in the founding of the Norwegian company A/S Anod, in which he held a 45% stake.
Finnish Civil War of 1918
As a Finnish citizen, Tigerstedt was called back to take part in the
Finnish civil warThe Finnish Civil War was a part of the national and social turmoil caused by World War I in Europe. The war was fought in Finland from 27 January to 15 May 1918, between the forces of the Social Democrats led by the People's Deputation of Finland, commonly called the "Reds" , and the forces of...
of 1918, and on 14 February 1918 he was on his way back to Finland. After the cessation of the hostilities, he participated in the
victory paradeA victory parade is a type of parade held in order to celebrate a victory. Because of that, victory parades can be divided into military victory parades and more frequent sport victory parades....
on 16 May 1918, but then returned to Denmark, where he married Ingrid Lignell in 1919. Their son Carl Axel Waldemar was born in 1921. However, their marriage soon began to deteriorate, and they separated not long after the birth of their son.
Loss of German patents
During
World War IWorld War I , also known as the First World War, the Great War, and the War to End All Wars, was a global military conflict which involved most of the world's great powers, assembled in two opposing alliances: the Triple Entente and the Triple Alliance...
, Germany had invalidated all of Tigerstedts patents. After the war, he received compensation from the German Government, but this amount quickly became worthless due to the
hyperinflationIn economics, hyperinflation is inflation that is very high or "out of control", a condition in which prices increase rapidly as a currency loses its value....
in Germany during 1921 to 1923. In 1922, Tigerstedt moved his laboratory to Finland, and he founded a new company called “Tigerstedts patenter”, which however also failed.
Move to America
In 1923 Tigerstedt moved to America where he founded his last company, "The Tiger Manufacturing Co", to produce small
radio receiversThis article is about a radio receiver, for other uses see Radio .A radio receiver is an electronic circuit that receives its input from an antenna, uses electronic filters to separate a wanted radio signal from all other signals picked up by this antenna, amplifies it to a level suitable for...
and
cryptographic devicesCryptography is the practice and study of hiding information. Modern cryptography intersects the disciplines of mathematics, computer science, and engineering...
. The Mexican government purchased 2 of the cryptographic devices, and the radio receivers also sold relatively well. Tigerstedt also had the opportunity to meet with the great American inventor Thomas Alva Edison, who wrote a letter of recommendation for Tigerstedt to the director of the Department of Commerce.
Death
When it finally seemed that Tigerstedt was on the verge of commercial success, he was involved in an ultimately fatal car accident on April 20, 1924, when another car unexpectedly turned in front of the car Tigerstedt was travelling in. There were persistent rumours that a competitor had arranged for the accident, but there was never any proof of this. He succumbed to
tuberculosisTuberculosis is a common and often deadly infectious disease caused by mycobacteria...
exactly one year later, on April 20, 1925 in the New York
Fifth AvenueFifth Avenue is a major thoroughfare in the center of the borough of Manhattan in New York City, USA. The section of Fifth Avenue between 34th Street and 59th Street is one of the premier shopping streets in the world. Fifth Avenue serves as a symbol of wealthy New York and is consistently ranked...
hospital, possibly due to side effects from his injuries in the car accident. He wrote his last letter to his brother Göran, in which he described the state of his company, explained the structure of a new
membraneIn a loudspeaker, a diaphragm is the thin, semi-rigid membrane attached to the voice coil, which moves in a magnetic gap, vibrating the diaphragm, and producing sound...
that he was developing and stated that he was about to undergo a
kidneyThe kidneys are paired organs, which have the production of urine as their primary function. Kidneys are seen in many types of animals, including vertebrates and some invertebrates. They are part of the urinary system, but have several secondary functions concerned with homeostatic functions. ...
operation due to the spreading tuberculosis. Unfortunately, medical science was not advanced enough to be able to save his life. After his death, his brother traveled to America and brought home his ashes for burial in Helsinki. As with many inventors, Tigerstedt's inventions were never fully appreciated during his own life time.
Inventions
Tigerstedt experimented in many areas. He developed a new version of the
shotgunA shotgun is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called shot, or a solid projectile called a slug...
that could be fired using the
thumbThe thumb when a person is standing in the medical anatomical position is the lateral-most digit of the hand. The Medical Latin English adjective for thumb is pollical.-Bones:The thumb consists of three bones:* Distal phalanx...
s and that counted the number of shots fired. Unfortunately, he was perennially short of funds, and he did not have enough financial standing to file for a
patentA patent is a set of exclusive rights granted by a state to an inventor or their assignee for a limited period of time in exchange for a public disclosure of an invention....
.
Sound-On-Film technology
His greatest interest however, was in the field of sound recording, and he had developed a prototype for recording sound on a metal wire as early as 1912. He was convinced that he could find a way to record sound directly on the film. He started his first experients in
HelsinkiHelsinki is the capital and largest city in Finland. It is in the southern part of Finland, on the shore of the Gulf of Finland, by the Baltic Sea. The population of the city of Helsinki is , making it the most populous municipality in Finland by a wide margin...
using very primitive equipment. The sentence he attempted to record on film was in
GermanGerman is a West Germanic language, thus related to and classified alongside English and Dutch. It is one of the world's major languages and the most widely spoken first language in the European Union. Around the world, German is spoken by approximately 105 million native speakers and also by...
: "Grau ist alle Theorie. Grün ist nur des Lebens Baum". Finally, he succeeded and he called his
inventionAn invention is a new configuration, device, or process. Some inventions are based on pre-existing models or ideas and others are radical breakthroughs...
the "photomagnetophone". Unfortunately, his achievements did not gain any recognition, nor did he reap any financial gains from his invention, so he had to maintain a day job in order to earn a modest living and he could only continue his experiements during evenings and into the nights (and sometimes through the nights without getting any sleep).
After meeting his former school mate Alfred Nybom in
BerlinBerlin is the capital city and one of sixteen states of Germany. With a population of 3.4 million within its city limits, Berlin is Germany's largest city. It is the second most populous city and the eighth most populous urban area in the European Union...
, he succeeded in using Nybom's connections to gain access to a
researchResearch can be defined to be search for knowledge or any systematic investigation to establish facts. The primary purpose for applied research is discovering, interpreting, and the development of methods and systems for the advancement of human knowledge on a wide variety of scientific matters of...
laboratory and employment as an inventor. Film with audio was thought to be a genuinely interesting field of development, but Tigerstedts invention still needed development before it could be commercialized. There was as yet no technology available to broadcast (and amplify) the sound in a large movie theatre. Tigerstedt also enlarged his vision of
videoVideo is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.-History:...
transmissionIn telecommunications, transmission is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired or wireless...
in the future. He wrote: "There will come a time when people can sit at home and follow events in the world through a device I now call the 'electronic eye'. When people get used to film with sound, they will soon adopt the electric eye, or electrophtalmoscope". When his father learned of his thinking, he tried to persuade him to not let his imagination carry him away, " ... otherwise you will surely end your days in the
asylumA psychiatric hospital, sometimes known as an asylum, is a hospital specializing in the treatment of serious mental illness, usually for relatively long-term inpatients....
in Lapinlahti".
Tigerstedt returned to Germany in 1913, where he continued developing the photomagnetophone, but there was still no solution to the problem of amplifying sound. He experimented with early versions of the vacuum tube, and he eventuelly managed to amplify the sound, but with disappointing results.
Tigerstedt also continued developing the electrophtalmoscope. The prototype consisted of vibrating mirrors in both the sending and receiving ends, using the photoelectric properties of a
seleniumSelenium is a chemical element with the atomic number 34, represented by the chemical symbol Se, an atomic mass of 78.96. It is a nonmetal, chemically related to sulfur and tellurium, and rarely occurs in its elemental state in nature....
element at the sender, and a
lightLight is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye ....
source at the receiving end which was
modulatedModulation is the process of varying one waveform in relation to another waveform. In telecommunications, modulation is used to convey a message, or a musician may modulate the tone from a musical instrument by varying its volume, timing and pitch. Often a high-frequency sinusoid waveform is used...
using a
FaradayMichael Faraday, FRS was an English chemist and physicist who contributed to the fields of electromagnetism and electrochemistry....
-device. The received picture was supposed to be displayed on a movie
screenA projection screen is an installation consisting of a surface and a support structure used for displaying a projected image for the view of an audience. Projection screens may be permanently installed as in a movie theater, painted on the wall , semi-permanent or mobile, as in a conference room or...
. Two electrophtalmoscopes were built, and an experiment was conducted using an electrical cable running from
London[]London is the capital of England and the United Kingdom. It has been a major settlement for two millennia, and the history of London goes back to its founding by the Romans, when it was named Londinium. London's core, the ancient City of London, the 'square mile', retains its medieval boundaries...
to
BerlinBerlin is the capital city and one of sixteen states of Germany. With a population of 3.4 million within its city limits, Berlin is Germany's largest city. It is the second most populous city and the eighth most populous urban area in the European Union...
. Tigerstedt arranged several demonstration events and gained reputation as a knowleadgable scientist.
Improving on Lee De Forests vacuum tube
Tigerstedt also stubbornly continued to grapple with the problem of the early vacuum tubes, which were inefficient, expensive and prone to breaking. His German colleagues however, told him that the vacuum tubes could not be developed further and that there could be no solution to the problem with the weakness of amplification. Tigerstedt however, continued to experiment, as he was convinced that the vacuum tube was the solution to his invention of
talking moviesA sound film is a motion picture with synchronized sound, or sound technologically coupled to image, as opposed to a silent film. The first known public exhibition of projected sound films took place in Paris in 1900, but decades would pass before reliable synchronization was made commercially...
.
After many disappointments, Tigerstedt finally succeeded in substantially improving on the design of
Lee De ForestLee De Forest was an American inventor with over 180 patents to his credit. De Forest invented the Audion, a vacuum tube that takes relatively weak electrical signals and amplifies them. De Forest is one of the fathers of the "electronic age", as the Audion helped to usher in the widespread use...
, and he achieved an amplification effect many times that of the original vacuum tubes. His achievement was purely experimental, as there were no prior experience or
mathematicalMathematics is the science and study of quantity, structure, space, and change. Mathematicians seek out patterns, formulate new conjectures, and establish truth by rigorous deduction from appropriately chosen axioms and definitions....
models that he could have followed. This was a major step forward for Tigerstedt, and he was soon able to show a film with sound which was electrically amplified and broadcast through a speaker system. He had finally solved the most difficult practical problem of talking movies. Beginning in 1919, DeForest created his own sound-on-film system, which he called
PhonofilmIn 1919, Lee De Forest, inventor of the audion tube, filed his first patent on a sound-on-film process, DeForest Phonofilm, which recorded sound directly onto film as parallel lines. These parallel lines photographically recorded electrical waveforms from a microphone, which were translated back...
, and which may have used some of Tigerstedt's concepts.
Patent for Sound-On-Film technology and Expulsion from Germany
Tigerstedt was awarded the German patent number 309.536 on July 28, 1914 for his
sound-on-filmSound-on-film refers to a class of sound film processes where the sound accompanying picture is physically recorded onto photographic film, usually, but not always, the same strip of film carrying the picture. Sound-on-film processes can either record an analog sound track or digital sound track,...
process. Tigerstedt also patented his improvement of the
triodeA triode is an electronic amplification device having three active electrodes. The term most commonly applies to a vacuum tube with three elements: the filament or cathode, the grid, and the plate or anode...
vacuum valve, which consisted of improving the amplification effect by re-arranging the electrodes cylindrically in the tube, changing the
glassIn general Glass refers to a solid, brittle, transparent material, commonly used for windows, bottles, or eyewear. Examples of glassy materials include, but are not limited to, soda-lime glass, borosilicate glass, acrylic glass, sugar glass, Muscovy-glass, or aluminium oxynitride. The term glass...
mold to prevent
vacuumIn everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty...
loss and for using steel mirrors inside the tubes to prevent electrostatic
interferenceIn physics, interference is the addition of two or more waves that results in a new wave pattern.Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same...
.
One month later, he was called for an
interviewAn interview is a conversation between two or more people where questions are asked by the interviewer to obtain information from the interviewee.- Employment-related :* Job interview* Case interview...
to the German authorities, where he was declared an unwanted Russian citizen. Tigerstedt was then asked to leave the country within 3 days.
World War IWorld War I , also known as the First World War, the Great War, and the War to End All Wars, was a global military conflict which involved most of the world's great powers, assembled in two opposing alliances: the Triple Entente and the Triple Alliance...
had started. Finland was at this time part of the Russian empire, having been ceded to Russia after the
1808-1809 war between Sweden and RussiaThe Finnish War was fought between Sweden and Russia from February 1808 to September 1809. As a result of the war, the eastern third of Sweden was established as the autonomous Grand Duchy of Finland within the Russian Empire...
. As a consequence of the declaration of war between Russia and Germany, the German government invalidated all German patents held by citizens of enemy nations, including those of Tigerstedt.
Ultrasound experiments
Tigerstedt moved to
DenmarkDenmark is a Scandinavian country in Northern Europe and the senior member of the Kingdom of Denmark. It is the southernmost of the Nordic countries; southwest of Sweden and south of Norway, and it is bordered to the south by Germany. Denmark borders both the Baltic and the North Sea...
where he continued working on filmsound recording devices at the Petersen & Poulsen company. He befriended the Danish inventor
Valdemar PoulsenValdemar Poulsen was a Danish engineer. He developed a magnetic wire recorder in 1899.The magnetic recording was demonstrated in principle as early as 1898 by Valdemar Poulsen in his Telegraphone...
(1869 - 1942), who was the inventor of the telegraphone (steel wire magnetic recorder). Tigerstedt had also previously experimented with recording sound on a steel wire. Tigerstedt also experimented with transmitting spoken sound using a 30
kHzThe hertz is a unit of frequency. It is defined as the number of complete cycles per second. It is the basic unit of frequency in the International System of Units , and is used worldwide in both general-purpose and scientific contexts...
ultrasound which he attempted to transmit across the
JutlandJutland , historically also called Cimbria, forms the mainland part of Denmark. It has the North Sea to its west, Kattegat and Skagerrak to its north, the Baltic Sea to its east, and the Danish-German border to its south...
straits. The results however, were not promising. He also experimented with transmitting sound under water, which was more successful, and he was eventually granted a patent for this process.
Communication device
A
pilotAn aviator is a person who flies aircraft for pleasure or as a profession. The first recorded use of the term was in 1887 as a variation of the French 'aviation', from the latin 'avis', coined 1863 by G. de la Landelle in "Aviation ou Navigation Aérienne"...
had suggested to Tigerstedt that he should develop a device to allow two pilots to communicate when seated in a row, such as in an open bi-plane. Tigerstedt went on to invent a small communication device. The device had a very small ear-piece that could be plugged into the ear. Tigerstedt spent considerable time on designing the ear-piece. The resulting device was also found to be suitable for people who were hard of hearing, instead of using a large ear horn.
See also
- Tri-Ergon
The Tri-Ergon sound-on-film system was patented from 1919 on by German inventors Josef Engl , Hans Vogt , and Joseph Massolle . The name Tri-Ergon was derived from Greek and means "the work of three." In 1926, William Fox of Fox Film Corporation purchased the U. S...
- Phonofilm
In 1919, Lee De Forest, inventor of the audion tube, filed his first patent on a sound-on-film process, DeForest Phonofilm, which recorded sound directly onto film as parallel lines. These parallel lines photographically recorded electrical waveforms from a microphone, which were translated back...
- Vitaphone
Vitaphone was a sound film process used on features and nearly 2,000 short subjects produced by Warner Bros. and its sister studio First National from 1926 to 1930. This was not the original process. The first process was called Fuchessound. Vitaphone was the last, but most successful, of the...
- RCA Photophone
RCA Photophone was the trade name given to one of four major competing technologies that emerged in the American film industry in the late 1920s for synchronizing electrically recorded audio to a motion picture image. RCA Photophone was a sound-on-film, "variable-area" film exposure system, in...
- Photokinema
Photo-Kinema was a sound-on-disc system for motion pictures invented by Orlando Kellum.-1921 Introduction:The system was first used for a small number of short films, mostly made in 1921...
- Fox Movietone
The Movietone sound system is a sound-on-film method of recording sound for motion pictures which guarantees synchronisation between the sound and the picture. It achieves this by recording the sound as a variable-density optical track on the same strip of film used to record the pictures...
- Joseph Tykociński-Tykociner
- Sound film
A sound film is a motion picture with synchronized sound, or sound technologically coupled to image, as opposed to a silent film. The first known public exhibition of projected sound films took place in Paris in 1900, but decades would pass before reliable synchronization was made commercially...
- sound-on-disc
The term Sound-on-disc refers to a class of sound film processes using a phonograph or other disc to record or playback sound in sync with a motion picture...
- List of film formats
External links